#define _XOPEN_SOURCE /* glibc2 needs this */
#define _BSD_SOURCE /* for tm.tm_gmtoff */
#include <time.h>
#include <ctype.h>

#include "cache.h"
#include "revision.h"

/*
 * revision.h leaves the low 16 bits of the "flags" field of the
 * revision data structure unused. We use it for a "reachable from
 * this commit <N>" bitmask.
 */
#define MAX_COMMITS 16

static int show_edges = 0;
static int basemask = 0;

static unsigned long parse_time(const char *buf)
{
        char c, *p;
        char buffer[100];
        struct tm tm;
        const char *formats[] = {
                "%s",
                "%c",
                "%a %b %d %T %y",
                NULL
        };
        const char **fmt = formats;

        p = buffer;
        while (isspace(c = *buf))
                buf++;
        while ((c = *buf++) != '\n' && c)
                *p++ = c;
        *p++ = 0;
        buf = buffer;
        memset(&tm, 0, sizeof(tm));
        do {
                const char *next = strptime(buf, *fmt, &tm);
                fmt++;
                if (next) {
                        if (!*next)
                                return mktime(&tm);
                        buf = next;
                }
        } while (*buf && *fmt);
        return mktime(&tm);
}
                

static unsigned long parse_commit_date(const char *buf)
{
        unsigned long time;

        if (memcmp(buf, "author", 6))
                return 0;
        while (*buf++ != '\n')
                /* nada */;
        if (memcmp(buf, "committer", 9))
                return 0;
        while (*buf++ != '>')
                /* nada */;

        time = strtoul(buf, NULL, 10);
        if (!time)
                time = parse_time(buf);
        return time;
}

static int parse_commit(unsigned char *sha1)
{
        struct revision *rev = lookup_rev(sha1);

        if (!(rev->flags & SEEN)) {
                void *buffer, *bufptr;
                unsigned long size;
                char type[20];
                unsigned char parent[20];

                rev->flags |= SEEN;
                buffer = bufptr = read_sha1_file(sha1, type, &size);
                if (!buffer || strcmp(type, "commit"))
                        return -1;
                bufptr += 46; /* "tree " + "hex sha1" + "\n" */
                while (!memcmp(bufptr, "parent ", 7) && !get_sha1_hex(bufptr+7, parent)) {
                        add_relationship(rev, parent);
                        parse_commit(parent);
                        bufptr += 48;   /* "parent " + "hex sha1" + "\n" */
                }
                rev->date = parse_commit_date(bufptr);
                free(buffer);
        }
        return 0;       
}

static void read_cache_file(const char *path)
{
        FILE *file = fopen(path, "r");
        char line[500];

        if (!file)
                die("bad revtree cache file (%s)", path);

        while (fgets(line, sizeof(line), file)) {
                unsigned long date;
                unsigned char sha1[20];
                struct revision *rev;
                const char *buf;

                if (sscanf(line, "%lu", &date) != 1)
                        break;
                buf = strchr(line, ' ');
                if (!buf)
                        break;
                if (get_sha1_hex(buf+1, sha1))
                        break;
                rev = lookup_rev(sha1);
                rev->flags |= SEEN;
                rev->date = date;

                /* parents? */
                while ((buf = strchr(buf+1, ' ')) != NULL) {
                        unsigned char parent[20];
                        if (get_sha1_hex(buf + 1, parent))
                                break;
                        add_relationship(rev, parent);
                }
        }
        fclose(file);
}

static void mark_sha1_path(struct revision *rev, unsigned int mask)
{
        struct parent *p;

        if (rev->flags & mask)
                return;

        rev->flags |= mask;
        p = rev->parent;
        while (p) {
                mark_sha1_path(p->parent, mask);
                p = p->next;
        }
}

/*
 * Some revisions are less interesting than others.
 *
 * For example, if we use a cache-file, that one may contain
 * revisions that were never used. They are never interesting.
 *
 * And sometimes we're only interested in "edge" commits, ie
 * places where the marking changes between parent and child.
 */
static int interesting(struct revision *rev)
{
        unsigned mask = marked(rev);

        if (!mask)
                return 0;
        if (show_edges) {
                struct parent *p = rev->parent;
                while (p) {
                        if (mask != marked(p->parent))
                                return 1;
                        p = p->next;
                }
                return 0;
        }
        if (mask & basemask)
                return 0;

        return 1;
}

/*
 * Usage: rev-tree [--edges] [--cache <cache-file>] <commit-id> [<commit-id2>]
 *
 * The cache-file can be quite important for big trees. This is an
 * expensive operation if you have to walk the whole chain of
 * parents in a tree with a long revision history.
 */
int main(int argc, char **argv)
{
        int i;
        int nr = 0;
        unsigned char sha1[MAX_COMMITS][20];

        /*
         * First - pick up all the revisions we can (both from
         * caches and from commit file chains).
         */
        for (i = 1; i < argc ; i++) {
                char *arg = argv[i];

                if (!strcmp(arg, "--cache")) {
                        read_cache_file(argv[2]);
                        i++;
                        continue;
                }

                if (!strcmp(arg, "--edges")) {
                        show_edges = 1;
                        continue;
                }

                if (arg[0] == '^') {
                        arg++;
                        basemask |= 1<<nr;
                }
                if (nr >= MAX_COMMITS || get_sha1_hex(arg, sha1[nr]))
                        usage("rev-tree [--edges] [--cache <cache-file>] <commit-id> [<commit-id>]");
                parse_commit(sha1[nr]);
                nr++;
        }

        /*
         * Now we have the maximal tree. Walk the different sha files back to the root.
         */
        for (i = 0; i < nr; i++)
                mark_sha1_path(lookup_rev(sha1[i]), 1 << i);

        /*
         * Now print out the results..
         */
        for (i = 0; i < nr_revs; i++) {
                struct revision *rev = revs[i];
                struct parent *p;

                if (!interesting(rev))
                        continue;

                printf("%lu %s:%d", rev->date, sha1_to_hex(rev->sha1), marked(rev));
                p = rev->parent;
                while (p) {
                        printf(" %s:%d", sha1_to_hex(p->parent->sha1), marked(p->parent));
                        p = p->next;
                }
                printf("\n");
        }
        return 0;
}